In this video, facilitators discuss how students might misinterpret a free body diagram and thereby make an incorrect prediction for the velocity graph of a fan cart after it has been given an initial push. This issue is contained in the video of student-facilitator interaction that is also available on this Web page.

Actors:
Use following key to figure out who is who:
OF = outside facilitator (off camera)
R = right
L = left
F = front
B = back

Transcript:

OF: Why was it presented that way, though?

RF: Because the gentle push is an additional initial force.

OF: Okay, and how might the students draw their free body diagram?

RF: They might have another force there for the push.

RB: It says, "draw a free body diagram for the cart-fan system AFTER it is no longer touching your hands.

OF: Right, so is there another force there after it is no longer touching...

RB and RF: No.

RF: But they might still think that.

RB: Right.

LF: the force...

OF: If they think that the force of the hand continues to act on the cart, how would they draw their free body diagram?

RB: They would have an extra (mumble: force?)

LF: there (drawing it on the page)

OF: ...they would have an extra force in there.

RB: Force in addition to the ... in the same direction as the fan.

OF: How would that correspond to their, um, ... how, if at all, would that affect their motion graphs?

RF: If they're thinking about it, as if there's another force, then their velocity should have a greater slope.